Field of the Invention
Embodiments of the present invention relate to battery devices. They are typically adapted to be mounted to the body of an electric tool. They may have a plurality of battery packs (also known as batteries) that serve as a power source in an electric tool.
Description of the Related Art
In recent years, there have been cordless electric tools that include a tool body to which a rechargeable battery pack (also known as a rechargeable battery) is mounted for serving as a power source. Rechargeable battery packs used for this purpose have been standardized so as to be commonly used as power sources for different kinds of electric tools. Therefore, many users retain a plurality of standardized rechargeable battery packs. Generally used standardized rechargeable battery packs have a rating voltage of 18 V for providing a power supply voltage of 18 V.
On the other hand, there are some electric tools, such as lawn mowers and chain saws, operating with a supply of 36 V. For these electric tools, the typical 18 V battery packs cannot be used. Therefore, in order to enable the 18 V battery packs to be used for these electric tools, DE102008040061A1 (also published as US2011/0147031A1) has proposed a battery device for converting a power supply with a voltage of 18 V into a power supply voltage with 36 V. The battery device of this publication is configured to enable two battery packs to be used as a power source. With this battery device, the 18 V battery packs can be used in place of a 36 V battery pack, so that it is possible to handle the two 18 V battery packs as if they are a 36 V battery pack. Therefore, the use of standardized battery packs can be employed in products that they were not originally created for.
However, the battery device disclosed in the above publication still has a problem whereby the increased size of the battery device caused by overlapping battery packs leads to difficulty in handling the electric tool.
Therefore, there has been a need in the art for a battery device that is improved in its handling property.